The long term goal of this proposal is to develop a clinically relevant therapeutic protocol to treat patients with limb threatening acute arterial insufficiency, to enhance skeletal muscle regeneration and restore limb function. Since ischemia reperfusion injury results in metabolic, thrombotic and inflammatory consequences which contribute to muscle injury and dysfunction, our research has focused on treatments that will simultaneously address these specific components. In addition, effective treatment protocols should provide benefit in a clinically relevant scenario, i.e. after the onset of ischemia. Poly ADP-Ribose Polymerase (PARP) deserves special attention in these studies because it is a nuclear and mitochondrial protein that modulates cellular transcription and metabolism through a variety of intracellular pathways. PARP inhibitors have been shown to alter endothelial dysfunction, tissue loss, metabolism and inflammation in models acute and chronic injury in normal and diabetic mice. In our lab, we have shown that administration of a PARP inhibitor after the onset of ischemia resulted in preservation of murine skeletal muscle structure, and energy levels;in addition, markers of inflammation were decreased as compared to untreated animals. While experiments provided herein clearly show that PARP inhibition modulates the acute response to hind limb ischemia reperfusion, for any therapeutic intervention to be of clinical benefit, it is important to demonstrate that there is long term functional, and anti-inflammatory benefit during the healing phase of reperfusion injury. It is also important to determine whether PARP inhibition modulates tissue injury in murine models which reflect the phenotype of patients who are at greatest risk for limb loss following an acute arterial occlusion, i.e. diabetic patients. Finally, since PARP inhibition appears to be experimentally feasible, it is important to develop a mechanistic understanding of how tissue recovery and muscle regeneration is achieved. Thus, this proposal is designed to provide mechanistic and translationally relevant information on how PARP inhibition modulates local muscle injury, metabolism, muscular regeneration and functional recovery in a murine model of moderate and severe ischemia reperfusion. Furthermore, we assess these indices of injury/healing/function in a "normal mouse" and murine model of human type two diabetes. PUBLIC HEALTH RELEVANCE: As risks factors such as diabetes mellitus continue to increase, the risk of limb loss due to vascular disease also increases. This proposal seeks novel translationally relevant approaches to decrease limb loss and encourage functional recovery following acute interruptions in extremity blood flow, which are common in patients with vascular disease.